Changes of natural environment in Kraków downtown - its chronology and directions. Case geoarchaeological studies of Krupnicza street site

Sediments exposed in a construction excavation form a sequence: alluvial deposits > black soil > made ground. Peat-like deposits, organic muds and occasionally sand occur between the soil and the made ground. High aeolization of alluvial sediments allows relating their age to the Late Vistulian. The sediments were eroded and in the washout at first organic muds were deposited and subsequently sands. The lowest layer, radiocarbon-dated at 4510±60 uncal. years BP (Gd-12724), can be probably linked to climate moistening at the transition between the Holocene Atlantic and the Subboreal period. Pollen grains found in muds, black soil and peat-like deposits reflect the changes of local plant cover from dominated by pine woodlands (at the transition between the Atlantic and the Subboreal period) to strongly deforested with single trees, meadows, small crop fields and gardens in the Medieval period. Palynological results describing the character of vegetation might have been influenced also by direct human activity on site, e.g. by storage of wood and branches (then used as construction material or fuel), crops, fodder or waste. Microartefacts found in soil suggest metal processing in the vicinity during the Bronze Age. In the made ground, which has been accumulating since the 14th century, quartz, clay minerals and micas were identified together with fragments of bricks, concrete, ceramics, bones, slag, charcoal, organic matter, limestone fragments and metals. Horizons enriched in slag fragments are also high in metals: Fe, Mn and Pb, which reveal a twofold increase in metal processing activity.