St Petersburg University scientists identify which soils were used to build the earth-and-timber Menshikov Bastion of the Peter and Paul Fortress

The history of St Petersburg began on 27 May 1703, when the first earth-and-timber fortress was laid on Zayachy Island at the mouth of the Neva River. In the conditions of the ongoing Northern War, it was important to quickly gain a foothold on the territory of what is now St Petersburg. A fortification was therefore erected in the shortest possible time, with Peter the Great himself having taken part in the development of its design. The rebuilding of the fortress in stone began in 1706. As a result, the remains of the earth-and-timber fortification were buried under a layer of bulk soil, which created favourable conditions for the conservation of the structure.

The research findings were presented at the conference titled "The Modern Museum of Urban Archaeology. Problems and Prospects of Creation".

In 2016, emergency response work was carried out at the Menshikov Bastion of the Peter and Paul Fortress. In the course of it, fragments of the earth-and-timber fortress were discovered. In 2017, excavations began, led by Vladimir Kildyushevsky, Research Associate at the Institute of the History of Material Culture of the Russian Academy of Sciences. He commissioned soil scientists from St Petersburg University to work on the study of the Bastion.

For us soil scientists, the peat and soddy blocks used for lining the earthen fortress, the so-called earth bricks, were of particular interest. They are a source of information about the natural environment of the object.

Professor Aleksey Rusakov, Acting Head of the Department of Soil Science and Soil Ecology at St Petersburg University

’Traditionally, palaeosol scientists study soils in situ, that is, in the place of their formation. That is how the maximum accuracy is achieved in the interpretation of their genesis and properties. We managed to study a rampart made of cut and displaced soil layers 40*20*10 cm in size, laid down with grass and fastened together with willow stakes,’ explained Professor Aleksey Rusakov, Acting Head of the Department of Soil Science and Soil Ecology at St Petersburg University.

A radiocarbon analysis of the Menshikov Bastion timber was done at the Laboratory of Palaeogeography and Geomorphology of Polar Countries and the World Ocean, St Petersburg University. That made it possible to reliably determine that the samples of timber taken at the fortification site during the excavations were approximately 510 years old accurate to within 70 years, due to the peculiarity of the methods used.

As the scientists note, the inaccessibility of buried soils for study is associated with the structural features of technogenic soils in St Petersburg. Since the inhabitants of the city had to constantly "reclaim" it from the sea, in many boroughs of the city there is a thick layer of bulk and alluvial soil, along with a cultural layer. So, Zayachy Island is one of the most artificially elevated areas of the city.

The formation of silt-humus and humus-peat material of the studied soils occurred under conditions of regular accumulation of fresh mineral material. It corresponds to the conditions of soil formation on the low, regularly flooded Neva islands. The samples found by the St Petersburg University scientists contain: traces of soil biota; fragments of the chitinous cover of invertebrates; and seeds.

Specialists from St Petersburg University and the Institute of Geography of the Russian Academy of Sciences studied the composition of biomorphs preserved in the soil (such as pollen, spores, and phytoliths). According to their findings, we can say that the studied soils were forming mainly under the vegetation of water meadows and coastal willows. The surrounding area was dominated by spruce-birch-pine forests with an admixture of alder. In the studied samples, traces of cultivated cereals and weeds were found, which is typical for the study area. It had already been partially cultivated by that time.

’Additionally, archaeologists from the Institute of the History of Material Culture of the Russian Academy of Sciences gave us a unique sample of soil from the sole of a boot found during the excavations. According to our estimates, the dirt from this boot is dried silt. There probably was a coastal reedbed at the construction site. The builder walked there, and silt stuck to the sole,’ said Mariia Fedorova, a postgraduate student in the Department of Soil Science and Soil Ecology at St Petersburg University.

These samples are unique because they show the state of the soil cover in the mouth of the Neva River in the early 18th century, before the foundation of the city and active anthropogenic impact. Archaeological work here makes it possible to study the soil cover of the pre-Petrine period, which is of particular interest to scientists.