Dirt road: A geomorphological and geochemical record of Late-Holocene human activity in the catchment of Lake Radacz (Central Pomerania, Poland)

Abstract

The paper offers a discussion of the record of human activity in the relief and sediments of a selected lake catchment in Central Pomerania in Poland. One of the basic markers of human activity here is a change in the lake-water level. The dropping level (on average, 1 m/100 years) made it possible for people to develop successively exposed stretches of land along the shore. An analysis of the Polish National Archeological Records and archival maps showed that human development and impact appeared in the lakeshore zone as early as the Neolithic. In Central Pomerania, the changes were especially intensive in the Late Holocene; in the catchment of the lake under study they included a 100% increase in the length of nearby roads. In the archives of its paleoenvironmental data, most traces have been left on farming terraces, while a poorly studied form of record of human activity is a dirt road running parallel to the shoreline. Geodetic and geochemical examination has revealed that the road is a stimulant of change. Its wheeled traffic mixes the accumulated and eroded material, and this causes changes in the shoreline section: the road cutting, which is 2 m wide, deepened, while material accumulates in the form of 0.5-m-wide lateral bars. The compaction of the material brings about changes in the structure of the ground or soil (its density, porosity, compactness, moisture), which affects its level of oxygenation and waterlogging, and, consequently, its iron content. To establish this, a speciation analysis was carried out using the Fe(III)/Fe(II) ratio. It was determined that the lower the ratio, the higher the susceptibility of land to deformation owing to an increase in soil density, a drop in its water capacity, reduction conditions, and the predominance of Fe(II). The research discussed here is only a pilot study, but the authors see extensive opportunities for using speciation analysis in geoarcheology.